fix crash (vesoft-inc#2042)

laura-ding · dutor · web-flow · commit eea740763e3d · 2020-04-02T14:40:28.000+08:00
Co-authored-by: dutor &lt;440396+dutor@users.noreply.github.com&gt;
diff --git a/src/graph/TraverseExecutor.cpp b/src/graph/TraverseExecutor.cpp
@@ -142,7 +142,7 @@ nebula::cpp2::SupportedType TraverseExecutor::calculateExprType(Expression* exp)
         case Expression::kInputProp: {
             auto* propExp = static_cast<const AliasPropertyExpression*>(exp);
             const auto* propName = propExp->prop();
-            if (inputs_ == nullptr) {
+            if (inputs_ == nullptr || !inputs_->hasData()) {
                 return nebula::cpp2::SupportedType::UNKNOWN;
             } else {
                 return inputs_->getColumnType(*propName);
diff --git a/src/graph/test/FetchVerticesTest.cpp b/src/graph/test/FetchVerticesTest.cpp
@@ -422,5 +422,17 @@ TEST_F(FetchVerticesTest, NonexistentProp) {
         ASSERT_EQ(cpp2::ErrorCode::E_EXECUTION_ERROR, code);
     }
 }
+
+TEST_F(FetchVerticesTest, EmptyInput) {
+    // YIELD has input prop, and input is empty
+    {
+        cpp2::ExecutionResponse resp;
+        auto query = "GO FROM 11 over like YIELD like._dst as id "
+                     "| FETCH PROP ON player 11 YIELD $-.id";
+        auto code = client_->execute(query, resp);
+        ASSERT_EQ(cpp2::ErrorCode::E_SYNTAX_ERROR, code);
+    }
+}
+
 }  // namespace graph
 }  // namespace nebula
